Competitive cyclists, including those competing in triathlons, competitive road races, cyclo-cross races, triathlon events and time trial events for example, seek better performing bicycles and bicycle components. Lightweight materials and advanced manufacturing techniques, for example, have been used to produce bicycles and bicycle components that improve the performance of competitive cyclists.
FIG. 1 shows a section of an example of a prior art bicycle wheel 1 that may be used by many competitive cyclists, and FIG. 2 shows a side elevation view of the prior art bicycle wheel of FIG. 1. The bicycle wheel 1 has a rim 2, a tire 3 sitting on the rim 2, a hub 4 having first and second flanges 7, 8, an axle 5 disposed in the hub, and a plurality of spokes 6 extending between the rim 2 and the hub 4. The spokes are generally but not necessarily thin in cross section, for example less than 10 mm at their maximum width. Each of these spokes must continually break the wind as the wheel rotates, resulting in flow separation and increased aerodynamic drag. Bicycle wheels and their subsystems for competitive cycling are generally regulated by competitive bicycling authorities. Examples of competitive bicycling authorities include but are not limited to the Union Cycliste Internationale (UCI), and various national triathlon authorities. The UCI, for example, has technical regulations for bicycle wheels used in competitive events including road races. UCI regulation 1.3.017, for example, states that the front fork separation must be no more than 105 mm and the rear fork separation must be no more than 135 mm. Spoked wheels are stipulated by bicycling authorities for many competitive bicycling events. Competitive bicyclists seek wheels with reduced aerodynamic drag, and thus increased performance. ‘Time trial’ or ‘triathlon’ bicycle wheels that have reduced aerodynamic drag are available. They may have a ‘solid’, ‘sandwich core’ or ‘hollow core’ construction. These wheels, however, are not spoked wheels as stipulated by the UCI and other bicycling authorities for certain competitive events and so can not be used in these competitive events.
FIG. 3 shows some stresses and forces experienced by a bicycle wheel. Radial forces 9 are the forces within a plane of the wheel that, generally speaking, are generated by the tensioning of the spokes. The radial forces 9 position the hub and the axle at on the wheel's axis (that is, in the vertical direction when the bicycle wheel is in use). The tensioned spokes 6 are inclined with respect to the plane of the wheel and so, generally speaking, also generate lateral forces 11. The lateral forces 11 laterally centre the hub so that the hub is positioned at the plane of the wheel (that is, position the hub in the horizontal direction) when the bicycle wheel is in use. The spokes 6 of some wheel may cross (that is, a wheel may have a crossed spoke lacing pattern) and consequently generate torsional forces 13 on the hub 4 and the rim 2. The net torsional force is zero on a stationary bicycle wheel. The net torsional force is not zero, however, when a bicycle rider applies force to the bicycle's pedals, the force being transferred via a bicycle chain to the hub 4 and then through the spokes 6 to the rim 2.
Competitive cyclists generally welcome bicycle wheels of improved performance, for example aerodynamic performance. Generally a stiffer bicycle wheel may be more responsive, a characteristic sought by competitive riders. Some bicycle wheels with improved performance have been proposed but not realised because their design parameters are either unknown or cannot be realistically achieved.
Bicycle wheel builders strive to engineer wheels that have the improved performance desired by competitive cyclists. Engineering a new wheel requires determining the stresses and forces within the wheel. Bicycle wheel builders may generally design a bicycle wheel using a simplified triangular truss model of the bicycle wheel. A three dimensional vector analysis of the simple triangular truss model may be used to determine the stresses and forces within the wheel.